1. Field of the Invention
The present invention relates to optical scanning and particularly to the use of special scanning techniques wherein high resolution near-surface images can be acquired rapidly in either a flat or a curved surface geometry.
2. Description of the Related Art
It has been previously demonstrated that ultrafast optical gating techniques can be used for defect detection in advanced ceramic materials. One of the most promising techniques, due to its low cost and ease of implementation, is optical coherence tomography (OCT). This technique is based on low coherence fiber interferometry and can produce high resolution subsurface images. However, to make devices based on OCT practical, the image acquisition time should be fast (hopefully approaching video rates). This was recognized and an OCT technique was modified so that the image acquisition time was reduced to .about.300 msec. This was accomplished at a price of reduced spatial resolution since the scattered light was not always collected at the focus of the lens. Another disadvantage of this technique is that the image is always collected in the X-Z plane, where Z represents the depth into the sample and X represents one transverse dimension.